The invention relates to text-editing and character display systems, and more particularly stored controlled systems featuring dual cursors, and variable margin and tabulation facilities.
Text editing and character display (or "word processing") systems are well known in the prior art, as represented by U.S. Pat. Nos. 3,501,746; 3,579,193; 3,675,208 and 3,755,789. Such systems are characterized by complex machine architectures, are difficult to program, and do not have the flexibility required in commerical products.
Stored program and microprogrammable controllers are also known in the prior art, and U.S. Pat. No. 3,731,280 is hereby incorporated by reference to illustrate such a controller and provide more detailed disclosure of the digital logic circuitry used in the present invention.
The prior art text editing and character display systems were not simple to use because they lacked fixed rule lines on the display, and the variable margin and tabulation facilities were not simply implemented and apparent to the user.